/*
	FileReader共有4种读取方法：
	1.readAsArrayBuffer(file)：将文件读取为ArrayBuffer。
	2.readAsBinaryString(file)：将文件读取为二进制字符串
	3.readAsDataURL(file)：将文件读取为Data URL
	4.readAsText(file, [encoding])：将文件读取为文本，encoding缺省值为'UTF-8'
*/
window['e'] = {
	rABS:false,//是否将文件读取为二进制字符串
	importXlsxToJSON:function(f,callback){
	    if(!f) {
	        return;
	    }
	    var reader = new FileReader();
	    reader.onload = function(e) {
	        var data = e.target.result;
	        var wb = undefined;
	        if(e.rABS) {
	            wb = XLSX.read(btoa(e.fixdata(data)), {//手动转化
	                type: 'base64'
	            });
	        } else {
	            wb = XLSX.read(data, {
	                type: 'binary'
	            });
	        }
	        callback(XLSX.utils.sheet_to_json(wb.Sheets[wb.SheetNames[0]]));
	    };
	    if(e.rABS) {
	        reader.readAsArrayBuffer(f);
	    } else {
	        reader.readAsBinaryString(f);
	    }
	},
	//文件流转BinaryString
	fixdata:function(data){
	    var o = "",
	        l = 0,
	        w = 10240;
	    for(; l < data.byteLength / w; ++l) o += String.fromCharCode.apply(null, new Uint8Array(data.slice(l * w, l * w + w)));
	    o += String.fromCharCode.apply(null, new Uint8Array(data.slice(l * w)));
	    return o;
	},
	tmpDown:undefined, //导出的二进制对象
	downloadJson(json,fileName,type){
	    var tmpdata = json[0];
	    json.unshift({});
	    var keyMap = []; //获取keys
	    //keyMap =Object.keys(json[0]);
	    for (var k in tmpdata) {
	        keyMap.push(k);
	        json[0][k] = k;
	    }
		var tmpdata = [];//用来保存转换好的json 
        json.map((v, i) => keyMap.map((k, j) => Object.assign({}, {
            v: v[k],
            position: (j > 25 ? e.getCharCol(j) : String.fromCharCode(65 + j)) + (i + 1)
        }))).reduce((prev, next) => prev.concat(next)).forEach((v, i) => tmpdata[v.position] = {
            v: v.v
        });
	    var outputPos = Object.keys(tmpdata); //设置区域,比如表格从A1到D10
        var tmpWB = {
            SheetNames: ['mySheet'], //保存的表标题
            Sheets: {
                'mySheet': Object.assign({},
                    tmpdata, //内容
                    {
                        '!ref': outputPos[0] + ':' + outputPos[outputPos.length - 1] //设置填充区域
                    })
            }
        };
        e.tmpDown = new Blob([e.s2ab(XLSX.write(tmpWB, 
            {bookType: (type == undefined ? 'xlsx':type),bookSST: false, type: 'binary'}//这里的数据是用来定义导出的格式类型
            ))], {
            type: ""
        }); //创建二进制对象写入转换好的字节流
	    var href = URL.createObjectURL(e.tmpDown); //创建对象超链接
	    $a = $("<a><span>下载</span></a>").attr("href",href).attr("download",fileName);
	    $a[0].click();
	    setTimeout(function() { //延时释放
	        URL.revokeObjectURL(e.tmpDown); //用URL.revokeObjectURL()来释放这个object URL
	    }, 100);
	},
	//字符串转字符流
	s2ab:function(s) { 
        var buf = new ArrayBuffer(s.length);
        var view = new Uint8Array(buf);
        for (var i = 0; i != s.length; ++i) view[i] = s.charCodeAt(i) & 0xFF;
        return buf;
    },
    // 将指定的自然数转换为26进制表示。映射关系：[0-25] -> [A-Z]。
    getCharCol:function(n) {
        let temCol = '',
        s = '',
        m = 0
        while (n > 0) {
            m = n % 26 + 1
            s = String.fromCharCode(m + 64) + s
            n = (n - m) / 26
        }
        return s
    }
}
